Image pickup apparatus, image capturing system, method for driving image pickup apparatus

ABSTRACT

An image pickup apparatus has a pixel array including a plurality of photoelectric conversion elements arranged in column and row directions, a first output unit configured to be driven by a first driving signal and to output first signals fed from at least some of the photoelectric conversion elements in the pixel array, and a second output unit configured to be driven by a second driving signal and to output second signals fed from at least some of the photoelectric conversion elements in the pixel array. The first driving signal and the second driving signal are asynchronous.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image pickup apparatuses, imagecapturing systems, and methods for driving image pickup apparatuses.

2. Description of the Related Art

Recently, image pickup apparatuses, such as digital cameras and videocameras, having a pixel array, such as a charge coupled device (CCD)image sensor or a complementary metal oxide semiconductor (CMOS) imagesensor, including a plurality of photoelectric conversion elements havebeen widely used. Such image pickup apparatuses generally have anelectronic view finder (hereinafter, abbreviated as “EVF”) function forrepeatedly displaying images captured using an image pickup element (forrecording) to allow users to check images of a subject. This EVFfunction generally uses a liquid crystal display device included in theimage pickup apparatuses. An image quality high enough to satisfy thelevel required for this function can be obtained using data from some ofthe pixels of the pixel array in displaying of the images. Accordingly,methods for reading out pixel data while thinning out some (rows orcolumns) of the pixels of the pixel array are often employed.

Execution of focusing and light metering of a subject at this time usingsignals fed from pixels (thinned-out pixels) whose data is not output asimages has been suggested (see Japanese Patent Laid-Open No.2005-277513). According to this suggestion, an image pickup apparatusincludes a first output unit configured to output pixel signals asvoltage values and a second output unit configured to output the pixelsignals as current values. The image pickup apparatus uses the outputvalues of the first output unit in displaying of images and uses theoutput values of the second output unit in focusing and light meteringoperations. In addition, the first and second output units can operateindependently and employ different readout cycles (a driving frequencyof the second output unit is set lower than that of the first outputunit to improve a signal-to-noise (S/N) ratio).

However, since the first and second output units synchronously operatein a technique disclosed in Japanese Patent Laid-Open No. 2005-277513,the operation performance may not be fully improved.

For example, different asynchronous signals are used as a driving signalof an image pickup apparatus and a driving signal (e.g., a motor drivingsignal) of an image capturing lens in a focusing operation and a facedetection operation. When a focusing operation (e.g., a servo AFoperation) or a face detecting operation is carried out insynchronization with the driving signal of the image pickup apparatus, asubject may not be tracked sufficiently.

In addition, when an exposure control operation (e.g., an AE operation)is carried out in synchronization with the driving signal of the imagepickup apparatus, a target exposure value of photoelectric convertingelements may not be finely adjusted according to the luminance of asubject.

SUMMARY OF THE INVENTION

Accordingly, in view of the above-described disadvantage, the presentinvention provides an image pickup apparatus, an image capturing system,and a method for driving an image pickup apparatus capable of fullyimproving the operation performance of the image pickup apparatus.

According to a first aspect of the present invention, an image pickupapparatus has a pixel array including a plurality of photoelectricconversion elements arranged in column and row directions, a firstoutput unit configured to be driven by a first driving signal and tooutput first signals fed from at least some of the photoelectricconversion elements in the pixel array, and a second output unitconfigured to be driven by a second driving signal and to output secondsignals fed from at least some of the photoelectric conversion elementsin the pixel array. The first driving signal and the second drivingsignal are asynchronous.

Additionally, according to a second aspect of the present invention, animage pickup apparatus includes a pixel array including a plurality ofphotoelectric conversion elements arranged in column and row directions,a first output unit configured to be driven by a first driving signaland to output first signals fed from at least some of the photoelectricconversion elements in the pixel array, and a second output unitconfigured to be driven by a second driving signal and to output secondsignals fed from at least some of the photoelectric conversion elementsin the pixel array. The first driving signal and the second drivingsignal are synchronous in a first image capturing mode but areasynchronous in a second image capturing mode.

Furthermore, according to a third aspect of the present invention, amethod for driving an image pickup apparatus having a pixel arrayincluding a plurality of photoelectric conversion elements arranged incolumn and row directions includes outputting, in response to a firstdriving signal, first signals fed from at least some of thephotoelectric conversion elements in the pixel array, and outputting, inresponse to a second driving signal, second signals fed from at leastsome of the photoelectric conversion elements in the pixel array. Thefirst driving signal and the second driving signal are asynchronous.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example configuration of an imagecapturing system according to an exemplary embodiment of the presentinvention.

FIGS. 2A and 2B are diagrams showing an example configuration layout ofan image pickup apparatus.

FIG. 3 is a diagram showing an example circuit configuration of a unitpixel in a pixel array.

FIG. 4 are waveform charts showing an example operation of an imagepickup apparatus.

FIG. 5 is a timing chart showing an example electronic rolling storageoperation of an image pickup apparatus.

FIG. 6 is a flowchart showing an example operation of a first outputunit.

FIG. 7 is a flowchart showing an example operation of a second outputunit.

FIG. 8 is a timing chart showing example operation timings of first andsecond output units.

FIG. 9 is a diagram showing an example configuration of an imagecapturing system according to another exemplary embodiment of thepresent invention.

FIGS. 10A and 10B are diagrams showing an example configuration layoutof an image pickup apparatus.

FIG. 11 is a flowchart showing an example operation of a second outputunit.

FIG. 12 is a timing chart showing example operation timings of first andsecond output units.

FIG. 13 is a diagram showing an example configuration of an imagecapturing system according to still another exemplary embodiment of thepresent invention.

FIGS. 14A and 14B are diagrams showing an example configuration layoutof an image pickup apparatus.

FIG. 15 is a flowchart showing an example operation of a second outputunit.

DESCRIPTION OF THE EMBODIMENTS First Exemplary Embodiment

An image capturing system 100 according to a first exemplary embodimentof the present invention will be described with reference to FIG. 1.FIG. 1 is a diagram showing an example configuration of the imagecapturing system 100 according to the first exemplary embodiment of thepresent invention.

The image capturing system 100 will now be described. An optical system110 forms an optical image of a subject onto an image pickup apparatus114, which will be described later. The optical system 110 is, forexample, an image capturing lens. The image capturing lens includes amotor (not shown) and a mechanism configured to drive the motoraccording to a processing result of a focus control unit 142, which willbe described later, to adjust the focus.

An optical driving unit 111 transmits information fed from the opticalsystem 110 to a system control unit 150. The optical driving unit 111also drives the optical system 110 to control operations of the opticalsystem 110 under the control of the system control unit 150. The opticaldriving unit 111 also includes a control signal generator. The controlsignal generator generates an optical driving signal for driving theoptical driving unit 111 under the control of the system control unit150. The control signal generator performs a motor driving operation,such as a focusing operation of the optical system 110 or the like, insynchronization with the optical driving signal. The optical drivingunit 111 supplies information on the optical driving signal to a timinggenerating unit 118.

A shutter 112 adjusts the exposure of the image pickup apparatus 114.The image pickup apparatus 114 converts an optical image of a subjectinto image signals. The image pickup apparatus 114 may be, for example,a charge coupled device (CCD) image sensor or a complementary metaloxide semiconductor (CMOS) image sensor. An internal configuration ofthis image pickup apparatus 114 will be described later with referenceto FIG. 3.

A low-pass filter (hereinafter, abbreviated as “LPF”) 115 eliminatesunnecessary wavelengths of light (unnecessary wavelengths that affectscolor reproduction) having passed through the optical system 110. TheLPF 115 is arranged between the shutter 112 and the image pickupapparatus 114.

An analog front end circuit (hereinafter, abbreviated as “AFE”) 116includes an analog-to-digital (A/D) converter for converting analogsignals output from the image pickup apparatus 114 into digital signals,a clamping circuit (e.g., an offset adjusting circuit), and adigital-to-analog (D/A) converter.

A digital front end circuit (hereinafter, abbreviated as “DFE”) 117receives a digital signal of each pixel through the AFE 116 and performsdigital processing, such as correction and rearrangement.

The timing generating unit 118 supplies clock signals and controlsignals to the image pickup apparatus 114, the AFE 116, and the DFE 117.For example, the timing generating unit 118 generates a first drivingsignal TGsig1 (TG1) and a second driving signal TGsig2 (TG2). The timinggenerating unit 118 is controlled by the system control unit 150. Thetiming generating unit 118 supplies the first driving signal TGsig1 andthe second driving signal TGsig2 to a first output unit and a secondoutput unit, which will be described later, respectively.

Here, the first driving signal TGsig1 and the second driving signalTGsig2 are asynchronous. The timing generating unit 118 also receivesinformation on the optical driving signal from the optical driving unit111. This allows the timing generating unit 118 to generate the seconddriving signal TGsig2 so that the second driving signal TGsig2 issynchronized with the optical driving signal for driving the opticaldriving unit 111. The optical driving signal is, for example, a lensdriving reference clock.

The timing generating unit 118 includes a first timing generator 118-1and a second timing generator 118-2. The first timing generator 118-1generates the first driving signal TGsig1, whereas the second timinggenerator 118-2 generates the second driving signal TGsig2.

An image processing circuit 120 performs predetermined image processing,such as pixel interpolation and color conversion, on data fed from theDFE 117 or data fed from a memory control circuit 122. The imageprocessing circuit 120 performs predetermined calculation on image dataif necessary. The image processing circuit 120 corrects signals outputfrom the image pickup apparatus 114 based on correction data stored in amemory 130, which will be described later. The image processing circuit120 also performs development processing, such as color conversion ofeach output signal, to convert the image data into an image.Additionally, the image processing circuit 120 includes a dataprocessing block 120-1. The image processing circuit 120 performs focusdetection and luminance detection based on images and supplies thedetection results to the system control unit 150 through the memorycontrol circuit 122. This allows the system control unit 150 to sendcontrol information to the optical driving unit 111 and to perform afocusing operation of the optical system 110.

The memory control circuit 122 receives image data from the DFE 117 orthe image processing circuit 120 and stores the image data in an imagedisplay memory 124, the memory 130, or a recording medium 1200.

The image display memory 124 temporarily stores image signalscorresponding to an image to be displayed on an image display unit 128,which will be described later.

The image display unit 128 includes a thin-film transistor liquidcrystal display (TFT-LCD) or the like. During an electronic view finder(EVF) operation, the image display unit 128 continuously displays images(movies) and allows users to check a movement of a subject.

The memory 130 stores captured still images and movies. The memory 130has a storage capacity sufficient enough to store a predetermined numberof still images or movies for a predetermined time.

A shutter control unit 140 drives the shutter 112 to adjust an aperturethereof.

The focus control unit 142 performs an auto focus (AF) operation.However, in this exemplary embodiment, since focusing and light meteringoperations are performed using some of signals output from the imagepickup apparatus 114, the focus control unit 142 is not used during theEVF operation. A temperature detecting unit 144 measures ambienttemperature in an image capturing environment and camera internaltemperature (e.g., temperature around the image pickup apparatus 114).The temperature detecting unit 144 is, for example, a thermometer.

A light metering control unit 146 performs an auto exposure (AE)operation. However, in this exemplary embodiment, since focusing andlight metering operations are performed using some of signals outputfrom the image pickup apparatus 114, the light metering control unit 146is not used during the EVF operation. By operating in cooperation with aflash 148, the light metering control unit 146 can have a flash-assistedimage capturing function.

The flash 148 (also referred to as a strobe) is used for capturingimages in darkness. The flash 148 also have a function for projecting AFauxiliary light.

The system control unit 150 controls the image capturing system 100. Thesystem control unit 150 includes, for example, a central processing unit(CPU).

A memory 152 stores constants, variables, and programs for use inoperations of the system control unit 150. The memory 152 stores presetcorrection data, such as, for example, shading correction data.

A display unit 154 displays operation statuses and messages according toprograms executed by the system control unit 150.

A nonvolatile memory 156, such as an electrically erasable programmableread-only memory (EEPROM), stores programs to be described later.

An operation unit 160 receives instructions entered by users. Theoperation unit 160 includes a shutter switch, an EVF operation switch, amode setting dial, a single shooting/continuous shooting switch, acontinuous-focusing-operation setting switch, an ISO speed settingswitch, and a power switch.

Through the shutter switch, two switches (SW1 and SW2) are turned ONstep-by-step according to the pressing depth of the shutter switch. At afirst step where the shutter switch is half pressed (at a step where theSW1 is turned ON), operations, such as an auto focus (AF) operation, anauto exposure (AE) operation, an auto white balance (AWB) operation, anda flash control (EF) operation, are performed. At a second step wherethe shutter switch is fully pressed (at a step where the SW2 is turnedON), the shutter control unit 140 controls the shutter 112. This causesan exposure operation for writing signals read out from the image pickupapparatus 114 in the memory 130 as image data through the AFE 116 andthe memory control circuit 122 and a development operation usingcalculation performed in the image processing circuit 120 and the memorycontrol circuit 122 to be performed. In addition, a series of recordingoperations of reading out image data from the memory 130, compressingthe image data, and writing the image data on the recording medium 1200is performed.

The EVF operation switch is used for continuously displaying images of asubject on the image display unit 128.

The mode setting dial is used for switching between various imagecapturing modes. The various image capturing modes include, for example,an automatic image capturing mode, a programmed image capturing mode, ashutter speed priority image capturing mode, an aperture priority imagecapturing mode, a manual image capturing mode, a night view imagecapturing mode, an astronomical image capturing mode, and a portraitimage capturing mode.

The single shooting/continuous shooting switch is used for switchingbetween a single shooting mode and a continuous shooting mode.

The continuous-focusing-operation setting switch is used for repeatingan AF operation and a lens focusing operation (generally, the focusingoperation is performed only once).

The ISO speed setting switch is used for setting an image capturingsensitivity (the ISO speed). The power switch is used for supplyingelectric power to each unit of the image capturing system 100. A powercontrol unit 182 includes a battery detecting circuit and a DC-DCconverter.

A power supply unit 186 includes a primary battery such as an alkalinebattery or a lithium battery, a secondary battery such as a NiCdbattery, a NiMH battery, or Li battery, or an AC adaptor. The recordingmedium 1200 is a removable medium, such as a memory card and a harddisk.

The image pickup apparatus 114 will now be described with reference toFIGS. 2A and 2B. FIGS. 2A and 2B are diagrams showing an exampleconfiguration layout of the image pickup apparatus 114.

The image pickup apparatus 114 includes a pixel array PA, verticalscanning circuits 77 a and 77 b, horizontal scanning circuits 76 a and76 b, a first output unit 71, and a second output unit 72.

The pixel array PA includes a plurality of unit pixel (one pixel) 60(more specifically, pixels 60(1-1) to 60(n-m)) arranged in a matrix.Each unit pixel 60 includes a photoelectric conversion element, whichwill be described later. That is, the pixel array PA includes aplurality of photoelectric conversion elements arranged in column androw direction. A charge storage operation of each pixel is controlled bysignals output from the vertical scanning circuits 77 a and 77 b.

The vertical scanning circuits 77 a and 77 b receive the first drivingsignal TGsig1 and the second driving signal TGsig2 from the timinggenerating unit 118, respectively. Here, the first driving signal TGsig1and the second driving signal TGsig2 are asynchronous. In addition, thesecond driving signal TGsig2 is generated by the timing generating unit118 to be synchronized with the optical driving signal for driving theoptical driving unit 111.

The vertical scanning circuit 77 a supplies signals, such as φTX, φRES,and φSEL, to pixels (first pixels) in each row of the pixel array PAbased on the first driving signal TGsig1. The vertical scanning circuit77 b supplies signals, such as φTX, φRES, and φSEL, to pixels (secondpixels) in each row of the pixel array PA based on the second drivingsignal TGsig2 through horizontal signal lines corresponding to eachsignal. Switches SWt_x_1, SWr_x_1, and SWs_x_1 or switches SWt_x_2,SWr_x_2, and SWs_x_2 set signals of the vertical scanning circuit 77 aor 77 b that are used as control signals on each horizontal line.

More specifically, when the switches SWt_x_1, SWr_x_1, and SWs_x_1 areturned ON, the switches SWt_x_2, SWr_x_2, and SWs_x_2 are turned OFF.This allows the vertical scanning circuit 77 a to supply signals, suchas φTX, φRES, and φSEL, to the pixels (the first pixels) in each rowthrough the corresponding horizontal signal lines on the basis of thefirst driving signal TGsig1.

In addition, when the switches SWt_x_2, SWr_x_2, and SWs_x_2 are turnedON, the switches SWt_x_1, SWr_x_1, and SWs_x_1 are turned OFF. Thisallows the vertical scanning circuit 77 b to supply signals, such asφTX, φRES, and φSEL, to the pixels (the second pixels) in each rowthrough the corresponding horizontal signal lines on the basis of thesecond driving signal TGsig2.

The switches SWt_x_1, SWr_x_1, and SWs_x_1 or the switches SWt_x_2,SWr_x_2, and SWs_x_2 are set ON/OFF through communication with thesystem control unit 150 (not shown). One of the switches SWt_x_1,SWr_x_1, and SWs_x_1 and the switches SWt_x_2, SWr_x_2, and SWs_x_2 areturned ON at one time.

Both of the horizontal scanning circuits 76 a and 76 b receive the firstdriving signal TGsig1 and the second driving signal TGsig2 from thetiming generating unit 118. Based on the first driving signal TGsig1,the horizontal scanning circuits 76 a and 76 b read out signals outputfrom pixels (first pixels) in each column of the pixel array PA tovertical output lines 67(i _(—) a) (where i is a natural number) andsupplies the signals to the first output unit 71 to be described later.In addition, based on the second driving signal TGsig2, the horizontalscanning circuits 76 a and 76 b read out signals output form pixels(second pixels) in each column of the pixel array PA to second verticaloutput lines 67(i _(—) b) (where i is a natural number) and supplies thesignals to the second output unit 72 to be described later.

Here, the vertical output lines 67 includes the first vertical outputlines 67(i _(—) a) (where i is a natural number) and the second verticaloutput lines 67(i _(—) b) (where i is a natural number). Each firstvertical output line 67(i _(—) a) is connected to, for example, everythree vertically arranged pixels (the first pixels). The second verticaloutput lines 67(i _(—) b) are connected to pixels (the second pixels)other than those connected to the first vertical output lines 67(i _(—)a), for example.

The first output unit 71 is driven by the first driving signal TGsig1through the horizontal scanning circuits 76 a and 76 b and outputs firstsignals fed from at least some pixels (the first pixels) in the pixelarray PA. More specifically, the first output unit 71 includes S-Ncircuits 75(i_1) (where i is a natural number) and output amplifiers74-1 and 74-2. Among the S-N circuits 75(i_1), those with odd number “i”and those with even number “i” are collectively referred to as S-Ncircuits 75 a and 75 b, respectively. The S-N circuits 75(i_1) aredriven by the horizontal scanning circuits 76 a and 76 b based on thefirst driving signal TGsig1 and supply the output amplifiers 74-1 and74-2 with signals fed from corresponding pixels to the first verticaloutput lines 67(i _(—) a). The output amplifiers 74-1 and 74-2 outputthe signals supplied from the S-N circuits 75(i_1) to a subsequent stageafter amplifying the signals.

The first signals are used in at least one of an image displayingoperation and an image recording operation. For example, the firstsignals are used in the EVF operation.

The second output unit 72 is driven by the second driving signal TGsig2through the horizontal scanning circuits 76 a and 76 b and outputssecond signals fed from at least some pixels (the second pixels) in thepixel array PA. More specifically, the second output unit 72 includesS-N circuits 75(i_2) (where i is a natural number) and output amplifiers74-3 and 74-4. The S-N circuits 75(i_2) are driven by the horizontalscanning circuits 76 a and 76 b based on the second driving signalTGsig2 and supply the output amplifiers 74-3 and 74-4 with signalsoutput from corresponding pixels (the second pixels) to the secondvertical output lines 67(i _(—) b). The output amplifiers 74-3 and 74-4output the signals supplied from the S-N circuits 75(i_2) to asubsequent stage after amplifying the signals.

The second signals are signals for use in acquisition of evaluation databased on which an image capturing condition is decided. For example, thesecond signals are used in a focusing operation (an AF operation).

Although pixels (the first pixels) whose signals are output by the firstoutput unit 71 and pixels (the second pixels) whose signals are outputby the second output unit 72 are different from one another in FIG. 2,these pixels may be the same pixels. When the first and second outputunits 71 and 72 output signals from the same pixels, the first andsecond output units 71 and 72 output signals at different times.

The unit pixel 60 included in the pixel array PA will now be describedwith reference to FIG. 3. FIG. 3 is a diagram showing an example circuitconfiguration of the unit pixel 60 included in the pixel array PA.

A photoelectric conversion element 61 performs photoelectric conversionand a charge storage operation for storing a charge (signal)corresponding to an optical image of a subject. The photoelectricconversion element 61 may be, for example, a photodiode (hereinafter,abbreviated as PD).

A transfer switch (hereinafter, abbreviated as TX) 62 may be, forexample, a transistor. Upon the signal φTX supplied to a gate thereofbecoming active, the TX 62 is turned ON and transfers the charge(signal) stored by the photoelectric conversion element 61 to a floatingdiffusion 64, which will be described later.

The floating diffusion (hereinafter, abbreviated as FD) 64 serves as acapacitor. The FD 64 holds the charge stored in the PD 61 andtransferred through the TX 62 and generates voltage (a signal)corresponding to an amount of the charge.

An amplifier 65 operates as, for example, a source follower. Theamplifier 65 amplifies the voltage corresponding to the charge held bythe FD 64 and outputs the voltage to the vertical output line 67, whichwill be described later.

A selection switch 66 is, for example, a transistor. Upon the signalφSEL supplied to a gate thereof becoming active, the selection switch 66is tuned ON and allows the voltage (signal) amplified by the amplifier65 to be output to the vertical output line 67.

The vertical output line 67 supplies a signal (voltage) output from theamplifier 65 to the first output unit 71 or the second output unit 72.

A reset switch 63 resets a potential of the FD 64. The reset switch 63is, for example, a transistor. Upon the signal φRES supplied to the gatethereof becoming active, the reset switch 63 is turned ON and resets thepotential of the FD 64.

An operation of the image pickup apparatus 114 will now be describedwith reference to FIG. 4. FIG. 4 are waveform charts showing an exampleoperation of the image pickup apparatus 114. FIG. 4 shows a signal to besupplied to pixels in a predetermined row (the n-th row) and a signal tobe supplied to pixels in a row following the predetermined row (the(n+1)th row).

At a time T0, the vertical scanning circuits 77 a and 77 b set signalsφRES(n) and φTX(n) active. This triggers the start of resetting ofpixels in the n-th row. More specifically, the reset switch 63 of apixel in the n-th row resets the potential of the FD 64 and resets thepotential of the photoelectric conversion element 61 through thetransfer switch 62 (dumps the stored charge).

At a time T1, the vertical scanning circuits 77 a and 77 b set thesignals φRES(n) and φTX(n) inactive. At this time, the photoelectricconversion element 61 starts a charge storage operation.

At a time T2, the vertical scanning circuits 77 a and 77 b set thesignal φTX(n) active to transfer the charge stored in the photodiode 61to the FD 64. More specifically, a period between T1 and T2 correspondsto an exposure time (a charge storage time) of the image pickupapparatus 114.

At a time T3, the vertical scanning circuits 77 a and 77 b set thesignal φTX(n) inactive to stop transferring the charge to the FD 64 andalso set the signal φSEL(n) active to output the voltage of the FD 64 tothe vertical signal line 67 after amplifying the voltage by theamplifier

At a time T4, the vertical scanning circuits 77 a and 77 b set thesignal φSEL(n) inactive. At the same time, the horizontal scanningcircuits 76 a and 76 b control the S-N circuits 75(i_1) and 75(i_2)based on the first driving signal TGsig1 or the second driving signalTGsig2. This causes the first output unit 71 to output the first signalfrom a pixel in the n-th row. Alternatively, the second output unit 72outputs the second signal from a pixel in the n-th row. At a time T5,the vertical scanning circuits 77 a and 77 b set the signals φRES(n) andφTX(n) active. This causes the pixels in the n-th row to be reset.

This is an exemplary single-horizontal-row storage-and-readout operationin the n-th row. Similarly, an exemplary single-horizontal-rowstorage-and-readout operation in the (n+l)th row is performed after apredetermined time GT from the operation in the n-th row as shown by thesignals φRES(n+1), φTX(n+1), and φSEL(n+1). More specifically, at a timeT0′, the vertical scanning circuits 77 a and 77 b set signals φRES(n+1)and φTX(n+1) active. This triggers the start of resetting of pixels inthe (n+1)th row. More specifically, the reset switch 63 of a pixel inthe (n+1)th row resets the potential of the FD 64 and resets thepotential of the photoelectric conversion element 61 through thetransfer switch 62 (dumps the stored charge). At a time T1′, thevertical scanning circuits 77 a and 77 b set the signals φRES(n+1) andφTX(n+1) inactive. At this time, the photoelectric conversion element 61starts a charge storage operation.

At a time T2′, the vertical scanning circuits 77 a and 77 b set thesignal φTX(n+1) active to transfer the charge stored in the photodiode61 to the FD 64.

At a time T3′, the vertical scanning circuits 77 a and 77 b set thesignal φTX(n+1) inactive to stop transferring the charge to the FD 64and also set the signal φSEL(n+1) active to output the voltage of the FD64 to the vertical signal line 67 after amplifying the voltage by theamplifier 65.

At a time T4′, the vertical scanning circuits 77 a and 77 b set thesignal φSEL(n+1) inactive. At the same time, the horizontal scanningcircuits 76 a and 76 b control the S-N circuits 75(i_1) and 75(i_2)based on the first driving signal TGsig1 or the second driving signalTGsig2. This causes the first output unit 71 to output the first signalfrom a pixel in the (n+1)th row. Alternatively, the second output unit72 outputs the second signal from a pixel in the (n+1)th row. At a timeT5′, the vertical scanning circuits 77 a and 77 b set the signalsφRES(n+1) and φTX(n+1) active. This causes the pixels in the (n+1)th rowto be reset. In this manner, an electronic rolling storage operation,which is an operation related to movies (continuous image capturing),such as an electronic view finder, is performed.

As shown in FIGS. 2A and 2B, pixels (the first pixels) whose signals areoutput by the first output unit 71 differ from pixels whose signals areoutput by the second output unit 72. Accordingly, the first and secondoutput units 71 and 72 may output signals simultaneously and inparallel. On the other hand, when the first and second output units 71and 72 output signals from the same pixels, the first and second outputunits 71 and 72 output signals at different times.

An electronic rolling storage operation of the image pickup apparatus114 will now be described with reference to FIG. 5. FIG. 5 is a timingchart showing an example electronic rolling storage operation of theimage pickup apparatus 114. In FIG. 5, a vertical axis represents aposition of each row, whereas a horizontal axis represents timing.

In each row, a first reset operation, a charge storage operation, atransfer operation, a readout operation, and a second reset operationare sequentially performed before a dummy charge storage operation (adummy storage). The period of the charge storage operation correspondsto the above-described charge storage time. Timings of the first resetoperation, the charge storage operation, the transfer operation, thereadout operation, and the second reset operation in a predetermined rowand a row following the predetermined row are shifted by a predeterminedtime GT. More specifically, the first reset operation corresponds to amechanical front curtain of a rolling shutter, whereas the readoutoperation corresponds to a mechanical rear curtain. Additionally, thecharge storage operation corresponds to a rolling storage operation.

An operation of the first output unit 71 will now be described withreference to FIG. 6. FIG. 6 is a flowchart showing an example operationof the first output unit 71.

At STEP S601, the timing generating unit 118 generates the first drivingsignal TGsig1 and supplies the first driving signal TGsig1 to thehorizontal scanning circuits 76 a and 76 b of the image pickup apparatus114. The first output unit 71 of the image pickup apparatus 114 isdriven by the first driving signal TGsig1 through the horizontalscanning circuits 76 a and 76 b and outputs, to the AFE 116, the firstsignals from at least some of the pixels in the pixel array PA. Thefirst signal is used in at least one of an image displaying operationand an image recording operation. The AFE 116 performs analog signalprocessing, such as A/D conversion, to generate first image data andoutputs the first image data to DFE 117. The DFE 117 supplies the firstimage data to the image processing circuit 120. The data processingblock 120-1 of the image processing circuit 120 detects, based on thefirst image data, an average output level Vout1 of the first image data.

At STEP S602, the image processing circuit 120 compares the averageoutput level Vout1 detected by the data processing block 120-1 with apreferable exposure output level Vtyp to determine whether the averageoutput level Vout1 is substantially equal to the preferable exposureoutput level Vtyp. If the image processing circuit 120 determines thatthe average output level Vout1 is substantially equal to the preferableexposure output level Vtyp, the process returns to STEP S601. If theimage processing circuit 120 determines that the average output levelVout1 is not substantially equal to the preferable exposure output levelVtyp, the process proceeds to STEP S603.

At STEP S603, the image processing circuit 120 supplies the systemcontrol unit 150 with information indicating that the average outputlevel Vout1 is not substantially equal to the preferable exposure outputlevel Vtyp through the memory control circuit 122. The system controlunit 150 controls the timing generating unit 118 to change a targetcharge storage time of pixels whose signals are output by the firstoutput unit 71 so that the average output level Vout1 approaches theoutput level Vtyp.

The timing generating unit 118 generates a charge storage control signalbased on the target charge storage time and supplies the control signalto the vertical scanning circuits 77 a and 77 b of the image pickupapparatus 114. The vertical scanning circuits 77 a and 77 b of the imagepickup apparatus 114 modify signals, such as φSEL, φRES, and φTX, basedon the charge storage control signal and supplies these signals topixels in each row. Through this operation, the charge storage time ofthe photoelectric conversion elements 61 is changed in pixels in eachrow.

At STEP S604, the timing generating unit 118 generates the first drivingsignal TGsig1 and supplies the first driving signal TGsig1 to thehorizontal scanning circuits 76 a and 76 b of the image pickup apparatus114. The first output unit 71 of the image pickup apparatus 114 isdriven by the first driving signal TGsig1 through the horizontalscanning circuits 76 a and 76 b and outputs, to the AFE 116, the firstsignals fed from at least some of the pixels in the pixel array PA. TheAFE 116 performs analog signal processing, such as A/D conversion, onthe first signals to generate first image data and outputs the firstimage data to DFE 117. The DFE 117 supplies the first image data to theimage processing circuit 120. The data processing block 120-1 of theimage processing circuit 120 detects, based on the first image data, anaverage output level Vout1 of the first image data again.

At STEP S605, the image processing circuit 120 compares the averageoutput level Vout1 detected by the data processing block 120-1 with thepreferable exposure output level Vtyp to determine whether the averageoutput level Vout1 is substantially equal to the preferable exposureoutput level Vtyp. If the image processing circuit 120 determines thatthe average output level Vout1 is substantially equal to the preferableexposure output level Vtyp, the process returns to STEP S601. If theimage processing circuit 120 determines that the average output levelVout1 is not substantially equal to the preferable exposure output levelVtyp, the process proceeds to STEP S606.

At STEP S606, the image processing circuit 120 supplies the systemcontrol unit 150 with information indicating that the average outputlevel Vout1 is not substantially equal to the preferable exposure outputlevel Vtyp through the memory control circuit 122. The system controlunit 150 controls the shutter control unit 140 to change an opening(aperture) of the shutter 112 so that the average output level Vout1approaches the output level Vtyp.

At STEP S607, the timing generating unit 118 generates the first drivingsignal TGsig1 and supplies the first driving signal TGsig1 to thehorizontal scanning circuits 76 a and 76 b of the image pickup apparatus114. The first output unit 71 of the image pickup apparatus 114 isdriven by the first driving signal TGsig1 through the horizontalscanning circuits 76 a and 76 b and outputs, to the AFE 116, the firstsignals fed from at least some of the pixels in the pixel array PA. TheAFE 116 performs analog signal processing, such as A/D conversion, onthe first signals to generate first image data and outputs the firstimage data to DFE 117. The DFE 117 supplies the first image data to theimage processing circuit 120. The data processing block 120-1 of theimage processing circuit 120 detects, based on the first image data, anaverage output level Vout1 of the first image data.

At STEP S608, the image processing circuit 120 compares the averageoutput level Vout1 detected by the data processing block 120-1 with apreferable exposure output level Vtyp to determine whether the averageoutput level Vout1 is substantially equal to the preferable exposureoutput level Vtyp. If the image processing circuit 120 determines thatthe average output level Vout1 is substantially equal to the preferableexposure output level Vtyp, the process returns to STEP S601. If theimage processing circuit 120 determines that the average output levelVout1 is not substantially equal to the preferable exposure output levelVtyp, the process proceeds to STEP S609.

At STEP S609, the image processing circuit 120 supplies the systemcontrol unit 150 with information indicating that the average outputlevel Vout1 is not substantially equal to the preferable exposure outputlevel Vtyp through the memory control circuit 122. The system controlunit 150 controls the timing generating unit 118 to change a target gainvalue for pixels whose signals are output by the first output unit 71 sothat the average output level Vout1 approaches the output level Vtyp.

The timing generating unit 118 generates a gain control signal based onthe target gain value and supplies the control signal to the firstoutput unit 71 of the image pickup apparatus 114. The output amplifiers74-1 and 74-2 of the first output unit 71 change the gain based on thegain control signal. The timing generating unit 118 then returns theprocess back to STEP S601.

In this manner, the operation of the first output unit 71 is performedasynchronously and in parallel to an operation of the second output unit72.

Meanwhile, this operation sequence is terminated when an electronic viewfinder operation is terminated through the EVF operation switch or whenthe operation is shifted into another operation (e.g., a still imagecapturing operation in response to pressing of the shutter switch).

Although a sequence for sequentially and separately changing a chargestorage time, an aperture, and a gain value to adjust the exposure hasbeen described, the charge storage time, the aperture, and the gainvalue may be simultaneously changed according to an algorithm.

An example operation of the second output unit 72 will now be describedwith reference to FIG. 7. FIG. 7 is a flowchart showing an exampleoperation of the second output unit 72.

At STEP S701, the timing generating unit 118 generates the seconddriving signal TGsig2 and supplies the second driving signal TGsig2 tothe horizontal scanning circuits 76 a and 76 b of the image pickupapparatus 114. The second output unit 72 of the image pickup apparatus114 is driven by the second driving signal TGsig2 through the horizontalscanning circuits 76 a and 76 b and outputs, to the AFE 116, the secondsignals fed from some of the pixels in the pixel array PA. The secondsignals are for focusing and are used in, for example, a focusingoperation (an AF operation). The AFE 116 performs analog signalprocessing, such as A/D conversion, on the second signals to generatesecond image data and supplies the second image data to the DFE 117. TheDFE 117 supplies the second image data to the image processing circuit120. The data processing block 120-1 of the image processing circuit 120detects, based on the second image data, an average output level Vout2of the second image data.

At STEP S702, the image processing circuit 120 compares the averageoutput level Vout2 detected by the data processing block 120-1 with apredetermined output level Vcom to determine whether the average outputlevel Vout2 is substantially equal to the predetermined output levelVcom. If the image processing circuit 120 determines that the averageoutput level Vout2 is substantially equal to the predetermined outputlevel Vcom, the process proceeds to STEP S706. On the other hand, if theimage processing circuit 120 determines that the average output levelVout2 is not substantially equal to the predetermined output level Vcom,the process proceeds to STEP S703.

At STEP S703, the image processing circuit 120 supplies the systemcontrol unit 150 with information indicating that the average outputlevel Vout2 is not substantially equal to the predetermined output levelVcom through the memory control circuit 122. The system control unit 150controls the timing generating unit 118 to change a target gain valuefor pixels whose signals are output by the second output unit 72 so thatthe average output level Vout2 approaches the output level Vcom.

The timing generating unit 118 generates a gain control signal based onthe target gain value and supplies the control signal to the secondoutput unit 72 of the image pickup apparatus 114. The output amplifiers74-3 and 74-4 of the second output unit 72 change the gain based on thegain control signal.

At STEP S704, the timing generating unit 118 generates the seconddriving signal TGsig2 and supplies the second driving signal TGsig2 tothe horizontal scanning circuits 76 a and 76 b of the image pickupapparatus 114. The second output unit 72 of the image pickup apparatus114 is driven by the second driving signal TGsig2 through the horizontalscanning circuits 76 a and 76 b and outputs, to the AFE 116, the secondsignals fed from some of the pixels in the pixel array PA. The secondsignals are for focusing and are used in, for example, a focusingoperation (an AF operation). The AFE 116 performs analog signalprocessing, such as A/D conversion, on the second signals to generatesecond image data and supplies the second image data to the DFE 117. TheDFE 117 supplies the second image data to the image processing circuit120. The data processing block 120-1 of the image processing circuit 120detects, based on the second image data, the average output level Vout2of the second image data again.

At STEP S705, the image processing circuit 120 compares the averageoutput level Vout2 detected by the data processing block 120-1 with thepredetermined output level Vcom to determine whether the average outputlevel Vout2 is substantially equal to the predetermined output levelVcom. If the image processing circuit 120 determines that the averageoutput level Vout2 is substantially equal to the predetermined outputlevel Vcom, the process proceeds to STEP S706. On the other hand, if theimage processing circuit 120 determines that the average output levelVout2 is not substantially equal to the predetermined output level Vcom,the process returns to STEP S703.

At STEP S706, the image processing circuit 120 detects an averageintensity of high-frequency components in the second image data todetermine a contrast value P and supplies the contrast value P to thesystem control unit 150 through the memory control circuit 122. Thesystem control unit 150 accesses the optical driving unit 111 to acquireinformation on a position of the optical system 110. The system controlunit 150 stores, in the memory 130, association information forassociating the contrast value P and the position of the optical system110.

At STEP S707, the system control unit 150 controls the optical drivingunit 111 to drive the optical system 110 by a predetermined amount.

At STEP S708, the system control unit 150 determines whether a positionof the optical system 110 that gives a peak of the contrast value Pexists with reference to the association information. If the systemcontrol unit 150 determines that the position of the optical system 110giving the peak exists, the process proceeds to STEP S709. If the systemcontrol unit 150 determines that the position of the optical system 110giving the peak does not exist, the process returns to STEP S706.

At STEP S709, the system control unit 150 selects peak contrast Pmax anda position Lmax of the optical system 110 corresponding to the peakcontrast Pmax. The system control unit 150 then controls the opticaldriving unit 111 based on the position Lmax of the optical system 110corresponding to the contrast Pmax to drive the optical system 110. Thesystem control unit 150 then returns the process back to STEP S701.

In this manner, the operation of the second output unit 72 is performedasynchronously and in parallel to the operation of the first output unit71.

Operation timings of the first and second output units 71 and 72 willnow be described with reference to FIG. 8. FIG. 8 is a timing chartshowing example operation timings of the first and second output units71 and 72.

As shown by a chart (a) of FIG. 8, the first output unit 71 is driven bythe first driving signal TGsig1 through the horizontal scanning circuits76 a and 76 b and outputs, for each row, the first signals fed frompredetermined pixels (first pixels) to a subsequent stage in response tocompletion of a readout operation from the pixels.

As shown by a chart (b) of FIG. 8, the second output unit 72 is drivenby the second driving signal TGsig2 through the horizontal scanningcircuits 76 a and 76 b and outputs, for each row, the second signals fedfrom predetermined pixels (second pixels) to a subsequent stage inresponse to completion of a readout operation from the pixels.

In a focusing operation, different asynchronous signals are used as theoptical driving signal and the first driving signal TGsig1 for readingout the first signals. In this case, the first driving signal TGsig1 andthe second driving signal TGsig2 are asynchronous. More specifically,the second driving signal TGsig2 is not synchronized with the firstdriving signal TGsig1 but is synchronized with the optical drivingsignal. With this configuration, a subject can be sufficiently trackedin a focusing operation (e.g. a servo AF operation).

In addition, a cycle of the second driving signal TGsig2 is shorter thanthat of the first driving signal TGsig1. With this configuration, asubject can be sufficiently tracked even if a driving signal for afocusing operation (e.g. a servo AF operation) is faster than the firstdriving signal TGsig1. As a result, the operation performance can befully improved.

Second Exemplary Embodiment

An example image capturing system 200 according to a second exemplaryembodiment of the present invention will now be described with referenceto FIGS. 9, 10A, and 10B. FIG. 9 is a diagram showing an exampleconfiguration of the image capturing system 200 according to the secondexemplary embodiment of the present invention, whereas FIGS. 10A and 10Bare diagrams showing an example configuration layout of an image pickupapparatus 214.

Although a basic configuration of the image capturing system 200 issimilar to that of the first exemplary embodiment, the image capturingsystem 200 differs from the image capturing system according to thefirst exemplary embodiment in having the image pickup apparatus 214, anexposure calculating unit 255, and a timing generating unit 218.

As shown in FIGS. 11A and 10B, the image pickup apparatus 214 differsfrom the image pickup apparatus according to the first exemplaryembodiment in having a second output unit 272. The second output unit272 is driven by a second driving signal TGsig2 through horizontalscanning circuits 76 a and 76 b and outputs second signals fed from atleast some pixels (second pixels) in a pixel array PA. The secondsignals are for focusing and light metering and are used in, forexample, a focusing operation (an AF operation) and an exposure controloperation (an AE operation).

If the second signals according to the first embodiment are used inlight metering, an S/N ratio of an image is unpreferable and the imagemay lack the accuracy since a charge storage time for the second signalsis short and the gain level is increased.

On the other hand, in the second exemplary embodiment, the exposurecalculating unit 255 calculates a target exposure value of the pixelarray PA based on the second signals. The exposure calculating unit 255supplies information on the target exposure value to the timinggenerating unit 218 through a system control unit 150. The timinggenerating unit 218 generates an exposure control signal based on thetarget exposure value and supplies the control signal to verticalscanning circuits 77 a and 77 b of the image pickup apparatus 214. Thevertical scanning circuits 77 a and 77 b of the image pickup apparatus214 modify signals, such as φSEL, φRES, and φTX, based on the exposurecontrol signal and supplies these signals to pixels in each row. Throughthis operation, the charge storage time of the photoelectric conversionelements 61 is changed in pixels in each row. More specifically, thetiming generating unit 218 generates the second driving signal TGsig2 soas to change the charge storage time of the photoelectric conversionelements 61, which output the second signals, according to the targetexposure value calculated by the exposure calculating unit 255.

As shown in FIG. 11, an operation of the second output unit 272 differsfrom that of the first exemplary embodiment in the following points.FIG. 11 is a flowchart showing an example operation of the second outputunit 272.

At STEP S803, an image processing circuit 120 supplies the systemcontrol unit 150 with information indicating that an average outputlevel Vout2 is not substantially equal to a predetermined output levelVcom through a memory control circuit 122. The image processing circuit120 also detects the luminance of second image data, which is data basedon the second signals. The exposure calculating unit 255 receivesinformation on the luminance of the second image data from the imageprocessing circuit 120 through the memory control circuit 122 and thesystem control unit 150. The exposure calculating unit 255 calculates atarget exposure value of the pixel array PA based on the second signals(according to the luminance of the second image data). The exposurecalculating unit 255 supplies information on the target exposure valueto the timing generating unit 218 through the system control unit 150.

The timing generating unit 218 generates an exposure control signalbased on the target exposure value and supplies the control signal tothe vertical scanning circuits 77 a and 77 b of the image pickupapparatus 214. The vertical scanning circuits 77 a and 77 b of the imagepickup apparatus 214 modify signals, such as φSEL, φRES, and φTX, basedon the exposure control signal and supplies these signals to pixels(second pixels) in each row. Through this operation, the charge storagetime of the photoelectric conversion elements 61 is changed in pixels ineach row. More specifically, the timing generating unit 218 generatesthe second driving signal TGsig2 so as to change the charge storage timeof the photoelectric conversion elements 61, which output the secondsignals, in accordance with the target exposure value calculated by theexposure calculating unit 255.

Meanwhile, the operation of the second output unit 272 and an operationof a first output unit 71 are performed asynchronously and in parallel,which is the same and or similar to the first exemplary embodiment.

As shown in FIG. 12, operation timings of the first and second outputunits 71 and 272 differ from those according to the first exemplaryembodiment in the following points. FIG. 12 is a timing chart showingexample operation timings of the first and second output units 71 and272.

As shown by a chart (b) of FIG. 12, the second output unit 272 is drivenby the second driving signal TGsig2 through the horizontal scanningcircuits 76 a and 76 b. The second output unit 272 outputs, for eachrow, the second signals fed from predetermined pixels (second pixels) toa subsequent stage in response to completion of a readout operation fromthe pixels.

Here, the first driving signal TGsig1 and the second driving signalTGsig2 are asynchronous. With this configuration, data giving apreferable exposure level is determined by gradually extending thecharge storage time of the photoelectric conversion elements 61 when anexposure control operation (e.g., an AE operation) is performed (at thetime of acquisition of light metering data). Since the gain value is notincreased during this period, the light metering can be performed at anS/N ratio better than that of a case where the gain value is increased.In addition, fine adjustment of the storage time becomes easier and amore accurate result is obtained. More specifically, the target exposurevalue of the photoelectric conversion elements 61 can be controlledfinely in accordance with the luminance of a subject. As a result, theoperation performance can be fully improved.

Third Exemplary Embodiment

An example image capturing system 300 according to a third exemplaryembodiment of the present invention will now be described with referenceto FIGS. 13, 14A, and 14B. FIG. 13 is a diagram showing an exampleconfiguration of the image capturing system 300 according to the thirdexemplary embodiment of the present invention, whereas FIGS. 14A and 14Bare diagrams showing an example configuration layout of an image pickupapparatus 314.

Although a basic configuration of the image capturing system 300 issimilar to those of the first and second exemplary embodiments, theimage capturing system 300 differs from the image capturing systemsaccording to the first and second exemplary embodiments in including theimage pickup apparatus 314 and an image processing circuit 320 whichincludes a data processing block 320-1.

Referring to FIGS. 14A and 14B, the image pickup apparatus 314 differsfrom the image pickup apparatuses according to the first and secondexemplary embodiments in including a second output unit 372. The secondoutput unit 372 is driven by a second driving signal TGsig2 throughhorizontal scanning circuits 76 a and 76 b and outputs second signalsfed from at least some pixels (second pixels) in a pixel array PA. Thesecond signals are for focusing, light metering, and face detection andare used in, for example, a focusing operation (an AF operation), anexposure control operation (an AE operation), and a face detectionoperation.

The image processing circuit 320 performs a face detection operation fordetecting a face of a subject based on second image data.

In addition, as shown in FIG. 15, an operation of the second output unit372 differs from those of the first and second exemplary embodiments inthe following points. FIG. 15 is a flowchart showing an exampleoperation of the second output unit 372.

At STEP S1110, the image processing circuit 320 performs color detectionof a subject based on the second image data to extract a skin color area(face) of a subject.

At STEP S1111, the image processing circuit 320 identifies a position(pixels) of the extracted skin color area (face) as a face area. Throughthis operation, the image processing circuit 320 sets the identifiedface area as a focusing target area.

At STEP S1106, the image processing circuit 320 detects an averageintensity of high-frequency components in the face area (focusing targetarea) of the second image data to determine a contrast value P andsupplies the contrast value P to a system control unit 150 through amemory control circuit 122. The system control unit 150 also accesses anoptical driving unit 111 to acquire information on a position of anoptical system 110. The system control unit 150 stores, in a memory 130,association information for associating the contrast value P and theposition of the optical system 110.

In a face detection operation, different asynchronous signals are usedas an optical driving signal and a first driving signal TGsig1 forreading out first signals. In this case, the first driving signal TGsig1and the second driving signal TGsig2 are asynchronous. Morespecifically, the second driving signal TGsig2 is not synchronized withthe first driving signal TGsig1 but is synchronized with the opticaldriving signal. With this configuration, a subject can be sufficientlytracked in the face detection operation.

Although the operation for separately outputting signals from the firstand second output units has been described in the exemplary embodimentsof the present invention, the present invention is not limited to thisparticular operation. For example, signals of all pixels may be outputsequentially from the top pixel row in response to a first drivingsignal generated by a first timing generator during capturing of stillimages.

In addition, the operation of the second output unit is not limited toan operation for extracting data. For example, the second output unitmay thin out signals and output the signals or may be used fordisplaying of images as in the case of the first output unit.

Furthermore, although the first and second output units are configuredseparately in the exemplary embodiments of the present invention, thepresent invention is not limited to this particular configuration. Forexample, the first and second output units may commonly use horizontalscanning circuits. At this time, a configuration (or a sequence) inwhich the second output unit is disabled while the first output unit isbeing horizontally scanned may be employable. In addition, aconfiguration (or a sequence) in which the first output unit is disabledwhile the second output unit is being horizontally scanned isemployable.

At this time, the first and second output units may be used in differentimage capturing modes (e.g., an EVF display mode and a movie recordingmode).

Additionally, the first driving signal TGsig1 and the second drivingsignal TGsig2 may be synchronous in a first image capturing mode but maybe asynchronous in a second image capturing mode. Here, the first imagecapturing mode may be a mode in which, for example, a focusingoperation, an exposure control operation, and an AF operation are notperformed, whereas the second image capturing mode may be a mode inwhich, for example, a focusing operation, an exposure control operation,and an AF operation are performed. In this case, an operation of thetiming generating unit 118 can be simplified. More specifically, thetiming generating unit 118 may divides the counts of the second drivingsignal TGsig2 to generate the first driving TGsig1 in the first imagecapturing mode.

Similarly, by turning only switches SWt_x_1, SWr_x_1, and SWs_x_1 ON andsequentially controlling all pixels using the first driving signalTGsig1, all of output signals may be treated as the output of the firstoutput unit in the first image capturing mode.

In addition, only a case where the second output unit operates insynchronization with an optical driving signal (which is notsynchronized with the first driving signal) has been described in theexemplary embodiments of the present invention, the present invention isnot limited to this particular case. For example, the second output unitmay employ an exclusive driving reference signal.

With the above-described configurations, it is possible to improve theusability and the performance of observation operations, such asfocusing and light metering operations, which are performed at the sametime as displaying of movies, such as an EVF display operation, andrecording of the movies.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications and equivalent structures and functions.

This application claims the benefit of Japanese Application No.2007-105251 filed Apr. 12, 2007, which is hereby incorporated byreference herein in its entirety.

1. An image pickup apparatus comprising: a pixel array including aplurality of photoelectric conversion elements arranged in column androw directions; a first output unit configured to be driven by a firstdriving signal and to output first signals fed from at least some of thephotoelectric conversion elements in the pixel array; and a secondoutput unit configured to be driven by a second driving signal and tooutput second signals fed from at least some of the photoelectricconversion elements in the pixel array, wherein the first driving signaland the second driving signal are asynchronous.
 2. The apparatusaccording to claim 1, wherein the first signals are used in at least oneof an image displaying operation and an image recording operation,whereas the second signals are used in at least one of a focusingoperation, a light metering operation, and a face detection operation,and wherein a cycle of the second driving signal is shorter than that ofthe first driving signal.
 3. An image pickup apparatus comprising: apixel array including a plurality of photoelectric conversion elementsarranged in column and row directions; a first output unit configured tobe driven by a first driving signal and to output first signals fed fromat least some of the photoelectric conversion elements in the pixelarray; and a second output unit configured to be driven by a seconddriving signal and to output second signals fed from at least some ofthe photoelectric conversion elements in the pixel array, wherein thefirst driving signal and the second driving signal are synchronous in afirst image capturing mode but are asynchronous in a second imagecapturing mode.
 4. The apparatus according to claim 3, wherein the firstsignals are used in at least one of an image displaying operation and animage recording operation, whereas the second signals are used in atleast one of a focusing operation, a light metering operation, and aface detection operation, and wherein a cycle of the second drivingsignal is shorter than that of the first driving signal.
 5. An imagecapturing system comprising: an image pickup apparatus including, apixel array including a plurality of photoelectric conversion elementsarranged in column and row directions; a first output unit configured tobe driven by a first driving signal and to output first signals fed fromat least some of the photoelectric conversion elements in the pixelarray; and a second output unit configured to be driven by a seconddriving signal and to output second signals fed from at least some ofthe photoelectric conversion elements in the pixel array, wherein thefirst driving signal and the second driving signal are asynchronous; anoptical system configured to form an optical image onto the image pickupapparatus; and a timing generating unit configured to generate a firstdriving signal and a second driving signal, wherein the timinggenerating unit supplies the first driving signal and the second drivingsignal to the first output unit and the second output unit,respectively.
 6. The image capturing system according to claim 5,further comprising: an optical driving unit configured to drive theoptical system, wherein the timing generating unit generates the seconddriving signal so that the second driving signal is synchronized with anoptical driving signal for driving the optical driving unit.
 7. Theimage capturing system according to claim 5, further comprising: anexposure calculating unit configured to calculate a target exposurevalue of the pixel array on the basis of the second signals, wherein thetiming generating unit generates the second driving signal so that acharge storage time of the photoelectric conversion elements configuredto output the second signals is changed in accordance with the targetexposure value calculated by the exposure calculating unit.
 8. A methodfor driving an image pickup apparatus having a pixel array including aplurality of photoelectric conversion elements arranged in column androw directions, the method comprising: outputting, in response to afirst driving signal, first signals fed from at least some of thephotoelectric conversion elements in the pixel array; and outputting, inresponse to a second driving signal, second signals fed from at leastsome of the photoelectric conversion elements in the pixel array,wherein the first driving signal and the second driving signal areasynchronous.
 9. The method according to claim 8, wherein the firstsignals are used in at least one of an image displaying operation and animage recording operation, whereas the second signals are used in atleast one of a focusing operation, a light metering operation, and aface detection operation, and wherein a cycle of the second drivingsignal is shorter than that of the first driving signal.
 10. An imagecapturing system comprising: an image pickup apparatus including, apixel array including a plurality of photoelectric conversion elementsarranged in column and row directions; a first output unit configured tobe driven by a first driving signal and to output first signals fed fromat least some of the photoelectric conversion elements in the pixelarray; and a second output unit configured to be driven by a seconddriving signal and to output second signals fed from at least some ofthe photoelectric conversion elements in the pixel array, wherein thefirst driving signal and the second driving signal are synchronous in afirst image capturing mode but are asynchronous in a second imagecapturing mode; an optical system configured to form an optical imageonto the image pickup apparatus; and a timing generating unit configuredto generate a first driving signal and a second driving signal, whereinthe timing generating unit supplies the first driving signal and thesecond driving signal to the first output unit and the second outputunit, respectively.
 11. The image capturing system according to claim10, further comprising: an optical driving unit configured to drive theoptical system, wherein the timing generating unit generates the seconddriving signal so that the second driving signal is synchronized with anoptical driving signal for driving the optical driving unit.
 12. Theimage capturing system according to claim 10, further comprising: anexposure calculating unit configured to calculate a target exposurevalue of the pixel array on the basis of the second signals, wherein thetiming generating unit generates the second driving signal so that acharge storage time of the photoelectric conversion elements configuredto output the second signals is changed in accordance with the targetexposure value calculated by the exposure calculating unit.
 13. Theimage capturing system according to claim 10, wherein the first signalsare used in at least one of an image displaying operation and an imagerecording operation, whereas the second signals are used in at least oneof a focusing operation, a light metering operation, and a facedetection operation, and wherein a cycle of the second driving signal isshorter than that of the first driving signal.